1. Field of the Invention
This invention relates to livestock feeders, and in particular to a feeder which is operated by livestock and which dispenses feed at a predetermined flow rate.
2. Description of the Prior Art
In the field of animal husbandry, livestock feeders with gravity-induced feed flow are well known. A variety of feeder designs have been developed in an attempt to achieve accurate and reliable metering of feed with minimal wastage.
A common design for such gravity flow feeders included a base member or trough adapted for receiving feed thereon and a hopper or bin with a central aperture in its bottom for dispensing feed onto the trough or base member. See for example the Pax U.S. Pat. No. 2,513,200. In use, as feed on the trough or base member was consumed by livestock, additional feed flowed from the hopper or bin by gravity to replace that consumed. Theoretically, the flow rate with such feeders was self-limiting because feed flow through the hopper bottom aperture was controlled by the presence of feed already therebelow. However, in practice such feeders suffered from a number of disadvantages. Firstly, total blockages were common because the weight of the hopper contents was directed against its aperture, and feed tended to pack together thereat under pressure and prevent flow. This problem was compounded by the animals licking and moistening feed at the hopper bottom aperture, thus causing it to stick together and solidify.
To counteract such blockage problems, agitators have been introduced in gravity-flow feeders to break up individual feed particles. See for example, the Fouts U.S. Pat. No. 1,392,004 and the Wildgruber German Pat. No. 1,127,136 which disclose agitator means accessible by animals for facilitating feed flow. However, a characteristic of such animal-actuated agitators was that larger volumes of feed material cause greater resistance to movement and smaller pigs were less able to operate such devices. Thus, such feeders effectively discriminated against smaller pigs, retarded their growth, and caused size variations within a given group to become even more pronounced.
Another type of agitator mechanism is shown in the Casper et al U.S. Pat. No. 2,153,455, wherein the hopper itself is rotatable with respect to the base member. However, heavily loaded axles or bearings are required for supporting the rotatable portions of that hopper, and were susceptible to freezing and breakage as well as increased manufacturing costs.
A second problem with gravity-flow feeders was that feed subjected to the greatest force was expelled first, typically those portions positioned centrally within the hopper and above the aperture. Consequently, feed material adjacent the hopper sides remained there for a considerable period of time and was subject to spoilage and waste.
Thirdly, many gravity-flow feeders lacked means for constantly mixing the feed material to discourage livestock from sorting out the most palatable portion thereof and wasting the rest. The portions wasted by livestock often included the flour-like protein meal and expensive dietary supplements which are relatively fine and may be blown away or lost without detection. Swine in particular are known to have such feeding habits.
Fourthly, accurate adjustment of feed flow rate was relatively difficult with such prior art gravity flow feeders. A typical adjustment means comprised a "knife edge" type structure which was slidably movable to adjust the size of the hopper bottom aperture and thus control the rate of flow. See for example, my copending U.S. Patent application Ser. No. 125,831 for ANIMAL FEEDER WITH FLUTED JOINT, now U.S. Pat. No. 4,303,039. Such adjustment means, however, often resulted in either all or nothing feed flow rates. Blockages were possible because the entire weight of the feed material in the bin was directed against the opening, and if the adjustment means was opened sufficiently to allow constant flow, the rate was often excessive with resultant spoilage and waste. Also, the volume of feed material directly influenced its flow rate through an opening of a given size. Thus, a knife-edge adjustment setting for a full bin had to be continuously readjusted as the feed level declined to assure constant flow.
A fifth disadvantage was that HMC feed materials were not suited for many prior art gravity flow feeders because their higher moisture contents increased the problems associated with bridging and flow blockage and resisted movement of agitators. Also, the stickiness of HMC feeds tended to cause them to pack tightly together and solidify. It is thus desirable that modern livestock feeders be adapted for use with HMC feeds because they are nutritionally superior and save grain drying costs.
Finally, most prior art gravitiy-flow feeders lacked means for limiting further flow until that already present in the feed trough was consumed. Therefore, animals using such devices were allowed to "root" or play in the feed material and empty the bin without consuming those portions already present in the trough.
Prior art gravity flow feeders therefore tended to be relatively unreliable, wasteful, ineffectively adjustable, ill suited for HMC feed, complex in structure or in manufacture, or in need of frequent attention and adjustment.